1. Field of the Invention
This invention relates to computerized tomography imaging systems. In a primary application the invention relates to rapidly obtaining cross-sectional X-ray images so that moving organs can be studied.
2. Description of Prior Art
The instrumentation presently used in computerized tomography falls into two general categories. The first is a two-motion system where all of the projections required to reconstruct a cross-sectional image are obtained by a combination of linear and orbital scanning. At each angular position of the source with respect to the object a linear traverse is made. This is repeated at many angular positions until a complete set of projections are obtained. This two motion procedure is described in U.S. Pat. No. 3,778,614 issued Dec. 11, 1973.
The second general category employs angular or orbital motion only. A fan beam of radiation, including X-rays or gamma rays, is transmitted through the object. Both the X-ray source and fan-beam detector are rotated around the body so as to produce projection data over the full range of angles. This data is then used to provide a cross-sectional reconstruction of the object. Such a fan-beam computerized tomographic apparatus is disclosed and claimed in U.S. Pat. applications Ser. Nos. 528,024; 528,025; and 528,026 all filed Nov. 29, 1974 and assigned to the same assignee as the present invention.
Each of the two scanning systems described is unsuitable for the study of rapidly moving organs, such as the heart, because of the relatively long scan time. The second scanning system, employing oribital motion only, provides scans of approximately five seconds. This time is suitable for respiratory studies since it is within a normal breath-holding interval. Five seconds, however, is unsuitable for studying the cardiac or digestive organs where more rapid motions are involved. In addition, this second scanning system is subject to distorting artifacts since the detectors are not calibrated while a patient is being scanned.